/*
 * Copyright (c) 2004-2022, University of Oslo
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors 
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.hisp.dhis.parser.expression.function;

import static org.hisp.dhis.antlr.AntlrParserUtils.castClass;
import static org.hisp.dhis.parser.expression.antlr.ExpressionParser.ExprContext;

import org.hisp.dhis.parser.expression.CommonExpressionVisitor;
import org.hisp.dhis.parser.expression.ExpressionItem;

/**
 * Function if
 *
 * <pre>
 *
 * In-memory Logic:
 *
 *     arg0   returns
 *     ----   -------
 *     true   arg1
 *     false  arg2
 *     null   null
 *
 * SQL logic (CASE WHEN arg0 THEN arg1 ELSE arg2 END):
 *
 *     arg0   returns
 *     ----   -------
 *     true   arg1
 *     false  arg2
 *     null   arg2
 * </pre>
 *
 * @author Jim Grace
 */
public class FunctionIf implements ExpressionItem {
  @Override
  public Object evaluate(ExprContext ctx, CommonExpressionVisitor visitor) {
    Boolean arg0 = visitor.castBooleanVisit(ctx.expr(0));

    if (arg0 == null) {
      return null;
    }

    return (arg0) ? visitor.visit(ctx.expr(1)) : visitor.visit(ctx.expr(2));
  }

  @Override
  public Object evaluateAllPaths(ExprContext ctx, CommonExpressionVisitor visitor) {
    Boolean arg0 = visitor.castBooleanVisit(ctx.expr(0));
    Object arg1 = visitor.visit(ctx.expr(1));
    Object arg2 = visitor.visit(ctx.expr(2));

    if (arg1 != null) {
      castClass(arg1.getClass(), arg2);
    }

    return arg0 != null && arg0 ? arg1 : arg2;
  }

  @Override
  public Object getSql(ExprContext ctx, CommonExpressionVisitor visitor) {
    return " case when "
        + visitor.sqlBooleanVisit(ctx.expr(0))
        + " then "
        + visitor.castStringVisit(ctx.expr(1))
        + " else "
        + visitor.castStringVisit(ctx.expr(2))
        + " end";
  }
}
